Howdy,
Double check where you are grounding.
You say your connected using 6/3 wire.
You will want a ground somewhere. If that is your meter, or at the service panel at the house.
Because of the 600ft distance. Use the clamp on meter, usually has a few other options, and measure your line voltage, and the hertz. Bring up the generator to have the best results to where the power is used. That means the generator might be showing 248 volts and 65hz on it, but 600ft away is 239volts and 59hz.
The nomenclature is funny. 120/240, or a 220 appliance, or would say a 110 outlet, or 115v appliance. It also means that if you were using 3 phase electrical, the A/C would run on 2 pair giving you the 208v.
The biggest enemy is to keep a good 60Hz at the use area and voltage. 600ft will see some drop.
Watch and feel the 6/3. If its getting hot, you will want to go larger wire.
Separate #6 wires work, or W type cord
W-6-4C 6 Gauge Multi-Conductor Type W Portable Power Cable gives you 87amp capacity